Thermoregulation. During cold winters, bears are often dormant. Physiological processes aid...
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Transcript of Thermoregulation. During cold winters, bears are often dormant. Physiological processes aid...
Thermoregulation
During cold winters, bears are often dormant.
Physiological processes aid homeostasis, keeping the body temperature about 5ºC below normal. Body fat and dense fur provide insulation. Blood flow to extremities is reduced. Nitrogen-containing wastes are metabolized
differently.
Introduction
© 2012 Pearson Education, Inc.
Homeostasis is the maintenance of steady internal conditions despite fluctuations in the external environment.
Examples of homeostasis include thermoregulation—the maintenance of internal
temperature within narrow limits, osmoregulation—the control of the gain and
loss of water and solutes, and excretion—the disposal of nitrogen-containing
wastes.
Introduction
© 2012 Pearson Education, Inc.
Figure 25.0_2
Thermoregulation is the process by which animals maintain an
internal temperature within a tolerable range and
a form of homeostasis.
25.1 An animal’s regulation of body temperature helps maintain homeostasis
© 2012 Pearson Education, Inc.
Ectothermic animals gain most of their heat from external sources
and include many fish, most amphibians, lizards,
and most invertebrates.
Endothermic animals derive body heat mainly from their metabolism
and include birds, mammals, a few reptiles and fish,
and many insects.
25.1 An animal’s regulation of body temperature helps maintain homeostasis
© 2012 Pearson Education, Inc.
Heat exchange with the environment may occur by conduction—the transfer of heat by direct contact, convection—the transfer of heat by movement of air or
liquid past a surface, radiation—the emission of electromagnetic waves, or evaporation—the loss of heat from the surface of a
liquid that is losing some of its molecules as a gas.
25.2 Heat is gained or lost in four ways
© 2012 Pearson Education, Inc.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
Five general categories of adaptations help animals thermoregulate.
© 2012 Pearson Education, Inc.
Increased metabolic heat production occurs when hormonal changes boost the metabolic rate in
birds and mammals, birds and mammals shiver, organisms increase their physical activity, and honeybees cluster and shiver.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
© 2012 Pearson Education, Inc.
Figure 25.3_UN01
Insulation is provided by hair, feathers, and fat layers.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
© 2012 Pearson Education, Inc.
Circulatory adaptations include increased or decreased blood flow to skin and countercurrent heat exchange, with warm and
cold blood flowing in opposite directions.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
© 2012 Pearson Education, Inc.
Figure 25.3_1
Heat dissipation(Via ear flapping)
EvaporativeCooling
Evaporative cooling may involve sweating, panting, or spreading saliva on body surfaces.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
© 2012 Pearson Education, Inc.
Behavioral responses are used by endotherms and ectotherms and include
moving to the sun or shade, migrating, and bathing.
25.3 Thermoregulation involves adaptations that balance heat gain and loss
© 2012 Pearson Education, Inc.
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